Semiconductor memory devices are used in various electronic devices. For example, non-volatile semiconductor memory is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices and other devices. Electrical Erasable Programmable Read Only Memory (EEPROM) and flash memory are among the most popular non-volatile semiconductor memories. Non-volatile memories can store data without power supply for long periods of time, such as a year or more, but the act of writing data into such memories is slow, requiring microseconds.
Attempts have been made to enhance memory performance, by using “crested” barriers, with the potential barrier height peaking in the middle and decreasing toward the interfaces with the electrodes. Parabolic barriers and stepped barriers have been proposed, but suitable and practical configurations and methods of making the barriers have been lacking.